Consider the following code:
int** a;
const int** b;
b = a;
This code gives an error:
error C2440: '=' : cannot convert from 'int **' to 'const int **'
Conversion loses qualifiers
Why i am not able to perform the cast?
When operating simple pointers it works ok.
int* a;
const int* b;
b = a;
Suppose you were able to perform this cast. Consider:
const int n = 42;
const int* cp = &n;
int* p;
int** a = &p;
const int** b;
b = a; // hypothetical, doesn't compile
*b = cp; // equivalent to p = cp;
*p = 84; // equivalent to n = 84: oops
Therefore, allowing an implicit cast from int** to const int** would allow a program to violate const correctness.
